Furnace clean and tune. Cycled system, checked heat exchanger, found some rust and damage. Checked and cleaned burners and flame sensor, burners were extremely worn and rusted. Flame sensor was also very worn. Cleaned both as best as I could. Burners still very rusted. Checked gas pressures and adjusted to maximize efficiency. Checked levels of CO and XS air in exhaust. Normal levels found. No CO found in airstream. Found evidence of water leak from ac coil in blower compartment. Office to call in spring for possible ac clean. If cleaning is done and conditions require replacement, all fees that were charged for the ac work will be refunded if replacement is made. System is howling signs of heavy wearing. Average life of this unit is 14 years. Job complete.